(1). Field of the Invention
This invention relates to a method for the topical treatment of ocular pain following corneal surgery. More particularly, the invention relates to the topical ophthalmic use of a non-steroidal anti-inflammatory agent in combination with a steroid for treating post-operative pain associated with corneal reprofiling surgeries.
(2). Description of the Prior Art
Various surgical procedures are known for altering the geometry of the cornea to correct refractive errors in vision. Such surgical procedures include radial keratotomy (RK) which is intended to correct myopia caused by excessive corneal curvature. In this procedure, a series of incisions is made in the cornea, usually penetrating about 90 to 95% of the thickness of the cornea. The incisions radiate outwardly from the corneal center and allow the cornea to relax and to flatten out somewhat, thereby reducing or eliminating nearsightedness. Similar corneal reprofiling procedures such as incisional keratotomy (IK), in which the incisions are made in directions other than radial, have been employed to correct certain astigmatisms.
Until recently, such surgical procedures were commonly carried out using instruments such as diamond or steel knives and razors. However, the results achieved in corneal operations using mechanical instruments are not highly predictable or controllable in any given patient and some patients have encountered post-operative discomfort and moderate pain related to damaged ocular tissue caused by surgical abrasion.
Recently, new laser surgical techniques have been developed which ablate the cornea to alter its refractive properties or otherwise treat corneal abnormalities. These laser reprofiling techniques include phototherapeutic keratectomy (PTK) in which laser radiation is applied to the cornea with minimal heating effects to ablate or smooth the cornea and remove opacities. When used to ablate very thin layers of corneal tissue to alter the curvature of the cornea for reducing or eliminating myopia, hyperopia or astigmatism, the procedure is typically referred to as photorefractive keratectomy (PRK). These corneal reshaping operations are presently performed with a high energy excimer laser which emits ultraviolet (UV) radiation capable of removing corneal tissue in a precise and incremental manner without thermal damage to surrounding tissue. For further details on PRK techniques, reference is made to Marshall et al., "Photoablative Reprofiling Of The Cornea Using An Excimer Laser: Photorefractive Keratectomy," Lasers in Ophthalmology, Vol. 1, pp. 21-48 (1986). Also, U.S. Pat. No. 4,665,913 to L'Esperance describes a PRK procedure for changing the contour of the anterior surface of the cornea by directing pulses from an excimer laser in a scanning pattern that moves around the cornea.
In clinical trials of PTK and PRK procedures, patients typically experience significant ocular pain immediately following surgery, which usually persists until corneal re-epithelialization. Despite the post-operative use of cold compresses, bandage soft contact lenses, cycloplegics, narcotics and corticosteroidal ophthalmic agents, patients usually describe the pain as severe, sometimes throbbing in nature and associate it with a burning, stinging sensation, as well as photophobia, tearing and nasal congestion. Some patients have characterized this type of pain as the worst they have ever experienced.
A number of ophthalmic substances have been reported in the patent literature for the control or treatment of ocular inflammation. For instance, U.S. Pat. No. 4,829,088 to Doulakas describes a ophthalmic medicament containing diclofenac sodium in aqueous solution for the treatment of inflammation of the eye. Also, U.S. Pat. No. 4,960,799 to Nagy (assigned to Ciba-Geigy Corp.) discloses that diclofenac sodium in the form of an aqueous solution can be useful in the control of post-operative inflammation resulting from cataract removal. However, the patentee fails to mention post-operative pain. This may be due to the fact that the severity of pain associated with complex corneal surgeries of the type described hereinabove is not commensurate with the relatively moderate discomfort associated with cataract removal. Moreover, these prior art formulations when used alone were found to be less effective in treating ocular pain of the type associated with such corneal surgeries.
Hence, there exists a need for a post-operative method for treating the newly reprofiled surface of the cornea to attenuate the pain, burning, stinging, photophobia and other adverse sensations that often accompany corneal surgical procedures.